Re-examination of copper Chevrel-phase sulfides as cathode in lithium secondary batteries

As cathode of lithium secondary batteries, copper Chevrel-phase sulfide Cu4Mo6S8 (CMS) and its host cluster Mo6S8 (MS) were re-examined. These cells could be galvanostatically discharged up to x=4.2−5.0 (LixCMS) when the current density was 0.1 mA/cm2 with a cutoff voltage at 1.5 V. In a deep cycling test in MS and CMS carried out between 1.5 and 2.6 V at 0.5 mA/cm2, the cell discharge capacity remained fairly constant up to at least 250 cycles, except decreasing during a few initial cycles.